Question 9Steam Plants - 1st Asst/Chief

70% to pass

Which of the following actions takes place in the control circuit of an automatically fired auxiliary boiler when the desired steam pressure is obtained?

AA temperature sensing device opens the circuit breaker in the burner motor.

BThe high limit control secures power to the entire oil firing system.

CThe stack relay actuates the low limit control which breaks the ignition circuit.

DThe stack relay secures power to the high voltage side of the ignition transformer.

AI Explanation

The correct answer is B) The high limit control secures power to the entire oil firing system. When the desired steam pressure is obtained in an automatically fired auxiliary boiler, the high limit control activates to shut off power to the entire oil firing system. This is a safety mechanism to prevent the boiler from producing excessive steam pressure. The other answer choices do not accurately describe the actions that take place in the control circuit under these conditions. Options A, C, and D describe different control mechanisms that may be present, but they do not specifically address the high limit control securing power to the oil firing system when the desired steam pressure is reached.